


Bathtub

by YellowLipstick



Category: The Hobbit - All Media Types
Genre: Alternate Universe - Modern Setting, Brother/Brother Incest, Cloaca, Durincest, Explicit Sexual Content, Fluff, Hermaphrodites, Incest, M/M, Mermaid Kíli, Shameless Smut, Sibling Incest, Weird Biology
Language: English
Status: Completed
Published: 2019-12-29
Updated: 2019-12-29
Packaged: 2021-02-26 03:41:09
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,097
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22016830
Author URL: https://archiveofourown.org/users/YellowLipstick/pseuds/YellowLipstick
Summary: Kili transforms into a merman at every full moon and has fun with his brother, Fili, bantering and splashing him in turn, much to his amusement.
Relationships: Fíli/Kíli (Tolkien)
Comments: 5
Kudos: 22





	Bathtub

Loud splashes, slaps on the water, pervaded the tiny apartment while Fili gritted his teeth and forced his thoughts to more innocent avenues in the living room. He had almost succeeded when he heard his frustratingly adorable, little brother’s voice sing out, “Filiiiii…I’m hungry,” Kili finished with another loud slap to the water, surely sending waves overflowing and cascading out of the bathtub the merman was trapped in and onto their tile, bathroom floor.

Fili huffed in amused annoyance and grumped, “I told you not to splash, Ariel, it’s only more of a mess for me to clean up later,” though he was already rifling through their pantry to find something suitable for the merman, Kili could be so picky and temperamental at his time of the month-his monthly transformation from human to merman during the full moon.

“Don’t call me that! I’m not even a redhead,” Kili snapped back before crossing his arms testily and pouting in the tepid bathwater while he waited for Fili to bring him a snack.

Neither brother would have believed they could ever find themselves in this situation, surely mermaids and all such superstition was just that: superstition and make believe. So when their Uncle Thorin had approached them at Fili’s sixteenth birthday all those years ago to explain the family’s secret blessing-or curse, depending on how one looked at it-they had been dumbfounded. Apparently, many generations ago, one of their kin had fallen in love with a mermaid, had even married her and had children by her. Their children had been human in appearance but after they had reached maturity, on the full moon, had transformed into mer; and now, many generations later, it appeared the magical blood still ran through their line. Though it seemed to skip some of the descendants now, perhaps the magic was weakening over time, with no new mer spouses for their kin, just human. Fili’s birthdays and years had come and gone without any transformations, but when Kili had turned nineteen, the following full moon, he had transformed into a beautiful merman.

It had shocked them both, having not entirely believed their Uncle, and truly, Thorin said it had been a couple generations since any of their kin had ever actually transformed. He had seen his father transform as a small child before his death but that had been it. Though, there was no denying the truth of their family’s secret, when Kili had first transformed. The brothers had been tangled up in the sheets, Fili was nuzzling Kili’s naked chest as the brunette panted his way down from another orgasm with his big brother buried deep inside his body, when suddenly he had jumped as sparks seemed to zing from his spine to his toes. Fili had just finished pouring himself into Kili and pulled out easily, concerned for his lover and brother, while Kili writhed and moaned against the dirty bedding, clawing at his legs and saying they itched and stung terribly. Fili had gaped, wide-eyed, as his baby brother’s legs started sprouting azure, opalescent scales and began to morph together, to form one, long and powerful fish tail.

They hadn’t really known what to do and Fili ended up making a home for Kili in the bathtub. Kili still ate regular food while in mer form though he said it tasted odd to him, wrong somehow, and when Fili had once jokingly offered him fish-flakes from the local pet store he had laughed himself silly at the merman’s delighted reaction, munching them down like potato chips. Life really went on like normal for the brothers, nothing had much changed between them or in their daily lives, other than taking off about three to five days from work a month, right around the full moon. It wasn’t really a problem as they worked for their Uncle Thorin, in his coffee shop. The only thing they had to continue to keep a secret from their family was their romantic relationship; but as they had always been unnaturally close, their family had accepted their sometimes odd or inappropriate behavior long ago as just the antics of ‘Fili and Kili’, the cuddly and silly Durin brothers.

For Fili though, these days could be hard-literally. He and Kili had a very active and involved sex life, basically, they fucked like bunnies more often than not. They had not yet figured out how to have sex while Kili was in mer form and those days of transformation were upsetting to the normally close pair, not even really being able to cuddle while Kili was ensconced in their large bathtub. They knew, logically, there must be a way to have sex as their ancestor obviously had done. Though Kili had described feeling aroused, nothing hard had ever poked out from his tail, despite him feeling a strong pressure from the front; and he had never really had to use the bathroom in this form so it wasn’t like they even knew where that entrance was. Everything seemed to metabolize much slower for the mer than it did for humans. Either way, it wasn’t like Fili could really go to their Uncle for advice on fucking his baby brother while in mer form. So he was stuck looking at his beautiful brother, who was quite possibly ever more tempting as a merman, and being able to do nothing about his erotic daydreams of taking the merman roughly or even gently in their bathtub.

Fili sighed and grabbed the huge bottle of fish-flakes from the back of the pantry as well as the sushi he had recently bought from the fridge, they had never tried sushi before and he wondered if Kili would like it or not.

“If the tail fits, Ariel,” Fili teased his sulking brother while walking into the bathroom, laden with snacks.

Kili perked up when he smelled the sushi, “What’s that Fee?” before pulling a face, “Eew sushi? Really?”

Fili chuckled at the frowning brunette, “I know you don’t like sushi, but you’re a fish now, so…maybe your tastes have changed, I mean, I don’t see you eating goldfish pellets while you’ve got your legs,” he teased.

Fili huffed and reached his hand out, beckoning Fili close, “Fine, let me try,” he grumbled.

Fili plopped the first sushi roll into Kili’s waiting mouth obligingly and watched as the brunette’s face lit up, “These are great, Fee,” the merman said happily while chewing up a mouthful of the raw fish.

Fili smirked, “Of course you would love them, Fishy.”

“’M names not Fishy,” Fili garbled though a mouthful of sushi, his words muffled by his chewing, and causing Fili to pull a face when the merman sprayed bits of raw fish over the edge of the tub with his talking.

Fili left the small plate of sushi balanced on the edge of the large tub as well as the fish-flakes and went to get ready for bed. It was already so late and he could feel his eyes itching with tiredness despite the persistent erection straining his shorts at the site of his beautiful, merman brother in their bathtub-sushi spraying and all.

Fili had just changed into a fresh t-shirt and sleep pants when he went to brush his teeth. Kili was immersed happily in the water and perked up when Fili walked in, waving his tail languidly through the air, almost in a ‘come hither’ motion.

“Come here Fee,” Kili crooned from the bathtub.

Fili shook his head at the tempting merman and tried to ignore the cute, pouting faces Kili was making at him in the mirror. He un-capped the toothpaste and squirted some on his toothbrush before putting it in his mouth and turning away from the mirror in an effort to not see his seductive, little brother purring at him from the bathtub. Kili knew how sexy Fili though he was as a merman and also knew they could do nothing about it; surely they would have figured it out by now, it had been several years since the brunette had transformed for the first time. Kili had given him blow jobs and hand jobs while transformed before, but it just felt wrong when he couldn’t bring Kili pleasure in return, and afterwards they couldn’t really lay together-it all just upset Fili more than it was worth the quick orgasm. Many times he couldn’t even bring himself to masturbate, he just missed his brother’s presence too much.

“Filiiiii…Fee,” Kili hummed seductively, blowing rude, cute little kisses at Fili when the elder finally eyed his little brother irritably.

Fili spit the toothpaste out in the sink and rinsed before muttering, “You’ll be the death of me, Kee,” and straightening up, ready to go to bed.

“Come cuddle with me, Fee, we never cuddle like this,” Kili whined adorably, flipping the edge of his tail lightly against the surface of the water and splashing Fili softly, getting his sleep pants all wet.

“We-we’ve tried stuff before, Kee, you know it won’t work,” Fili grumbled half-heartedly while already stripping his clothes, he could deny his beloved nothing.

“I know that, Fee,” Kili responded quietly, his normally cheerful face taking on a suddenly gloomy expression, “I just, I just miss you. I want you to hold me, I need you,” he murmured softly.

Fili’s brow creased in concern, his baby brother was never very needy and rarely ever expressed his feelings so openly, without teasing, “Is everything okay, Kee?” he questioned in concern.

Kili brightened, “You’re just so cute, Fee, and I wanna snuggle with you,” he chirped happily from the bathtub as Fili stepped closer.

When Fili was right at the edge, Kili’s waving tail came down in a loud slap against the water, splashing Fili all over with the tepid, fishy water.

“Kili!” Fili spluttered, dripping everywhere.

Kili laughed musically, “Just getting you adjusted to the water, lover” he sung in amusement.

Fili huffed and plopped himself down into the bathtub before shifting the slippery merman into his arms, so that they were spooning in the large, soaker tub closely. The water was warm around them and Fili sighed in relief as his hardened cock finally started softening while his body relaxed against Kili’s in loving comfort.

Kili wiggled his hips and pushed his tail back against Fili’s semi-hard dick teasingly, “Thinking things, brother?”

Kili growled and nipped the cheeky brunette’s ear, “I’m always thinking things, especially about the rude merman that lives in my bathtub,” he grumbled.

“He sounds like fun,” Kili laughed before cozying himself back into Fili’s arms and humming happily, “Thanks Fee, sometimes I just miss you holding me,” he whispered.

Fili squeezed his arms tight around Kili and placed little kisses all along his exposed neck and jaw, “Love you, Kee,” he mumbled against the merman’s damp, warm skin.

“Love you more, Fili,” Kili chirped cutely, before lowering his voice to a mumble and saying, “Thanks for taking care of me, Fee, I’d be lost without you.”

“Hey now, you know I’ll always love you and take care of you, even if you’re half fish,” Fili teased with a soft poke to Kili’s slippery, lapis tail, “You’re everything to me, Kee.”

Kili sighed in content before flipping over and burrowing his face into Fili’s collarbone, humming out a hypnotic lullaby, and putting both of them to sleep in the bathtub as the water slowly lapped and cooled around their entwined bodies.

Sometime in the middle of the night, Fili woke all pruned and chilled, and left the bathtub much to Kili’s displeasure. Fili tried to ignore Kili’s unhappy whines echoing down the hall while he dried off and put on some dry, warm clothes. He brought a worn sleeping bag and a pile of towels back into the bathroom to create a little nest for himself at the base of the tub and settled in. Fili pulled the drain to the tub and ran warmer water in it for his shivering baby brother before shushing Kili’s lonely whimpers with soft kisses while interlacing their fingers over the edge of the tub. When the tub was filled with clean, warmer water, Kili settled back down and lay close to the edge with his arm dangling over, reaching down to Fili. Fili kept their fingers laced and snoozed in a ball on the floor, comfortable in the little nest he had made of the sleeping bag and towels. They slept the night through together, sometimes waking up and falling back asleep to the sounds of the other’s breathing, simply content once more as they had each other close by.

The next morning, Kili was irritable and entirely beside himself with itchy, twitchy sensations that demanded his mer body be satisfied in some way. He whined pitifully at Fili from the bathtub and sloshed around in discomfort, complaining that he tingled and itched, stung and ached, and overall just felt a building pressure he couldn’t figure out how to release. It was like in the past when he had described feeling aroused while in mer form, only this time was much worse. Fili wasn’t sure what had caused it, but felt guilty, wondering if it was his wandering around in the nude upon waking up and shedding his pajamas that had tipped his little brother over the edge while unable to do anything about it. After several hours of Kili moaning and whining in the bathtub, slapping his tail in irritation at the water, and squirming up against the slippery porcelain as if to find friction in the shallow basin; Fili finally just hopped back into the tub with Kili and tried to cuddle the wiggling merman, hoping to calm him down. 

Kili only keened and whined miserably while sliding his tail back and forth over Fili’s soft groin, seeking for a friction he couldn’t find.

“Shhh, baby, you’ve just got to calm down. You only have one more day like this and then I’ll make it all up to you,” Fili soothed while Kili only thrashed around and moaned uncomfortably.

Fili tried to still the brunette’s wild motions by wrapping his arm over the top portion of the merman’s thick, azure tail, even with Kili’s hipbones. Kili’s tail twitched and his whole body shivered against Fili as the blonde’s arm brushed against the front of the mer’s tail, eliciting delicious tingles throughout his whole body, and causing his dorsal fins to curl in pleasure.

“Kee?” Fili questioned anxiously, mistaking Kili’s quaking for discomfort, and hoping he hadn’t hurt his little brother by grabbing at his tail.

“M-more Fee,” Kili moaned breathlessly, rubbing himself back against Fili in search of more touches to his tail.

Fili had no idea what was going on, but the way his beautiful brother was rubbing against him was quickly hardening his sex, and the blonde groaned while he petted his palm against the front of Kili’s tail passionately, eliciting more loud moans from the brunette.

“You like that, baby?” Fili murmured huskily against Kili’s shoulder, ecstatic that he seemed to be able to provide sexual pleasure in some form for his brother like this.

“Yes Fee…Mpfh, Filiiiii…” Kili moaned out hoarsely, his shouts echoing around their tiny bathroom and surely disturbing the neighbors.

Suddenly Fili’s hand caught at a small bulge in the front of Kili’s tail, growing more pronounced by the minute, though they had never noticed anything protruding from the mer’s tail before. Fili rubbed at the hardened lump curiously and Kili stiffened in his arms before thrashing his tail wildly, splashing water everywhere so that there was barely any left in the tub, and keening breathlessly in response to the blonde’s touches. The place Fili was touching was exactly where Kili felt the strong pressure emanating from, pulsing waves of desire and arousal all down his tail and into his sensitive fins. He wasn’t sure why he hadn’t felt this strongly before, hadn’t felt the pressure so pointedly, or why they had never explored touching his tail like this, sexually, but was glad they were finally exploring this now. Kili had borne years of aroused discomfort with no seeming outlet while a merman; perhaps fueled by a lack of exploration on their part, as they just assumed the merman didn’t have a penis appendage in this form, and they had no clue where to begin searching for any other orifices. Now though, Kili felt he would come apart if he couldn’t find release in some form, and Fili’s touches against his tail felt so very good.

Kili groaned gutturally when Fili’s questing fingers rubbed at the hardened bump in his groin area firmly, confidently now, and somehow slipped into a hidden slit in the scales that must have been there all along-just camouflaged very well amongst the dark, azure flesh. With a gasp, and a tremendous, overwhelming release of pressure, Kili’s long, curved cock slipped out of the slit Fili’s fingers were probing and unconsciously holding open, allowing for the merman’s hardened appendage to finally push free of the secret pouch in the front of his tail.

“O-oh God, Fee…” Kili moaned blissfully as Fili exclaimed in happy surprise, “Kee!” before fisting the merman’s hardened length and moving up and down with delicious squeezes and rubs.

Fili couldn’t believe he finally was able to pleasure his brother when he was transformed as a merman, and his heady realization echoed through his lust-hazed mind over and over, filling him with warm joy and utter relief that he could be there for his lover all the time now, physically and emotionally. The elder jacked Kili’s long dick in his fist heatedly while rubbing his own erection against the back of the mer’s tail, slipping and sliding wetly over the soft scales. Kili was panting and puffing quick breaths; his tail fins were curling in pleasure against Fili’s legs, and as he arched his back and cried out suddenly, the blond knew his lover was close to cumming. Suddenly Fili’s hips stuttered and the crown of his erection caught against a new, fluttering opening in the back of Kili’s tail; the little slit was dripping and squirting warm, sticky fluid all over Fili’s hard sex.

Kili was keening mindlessly and thrusting his hips forward into Fili’s hand, when the blonde curiously pushed a finger into the newly revealed opening in the back of Kili’s tail. Kili’s fluids gushed around Fili’s finger and the brunette screamed in pleasure and thrashed his tail wildly against the hot, blissful penetration as he came all over his elder brother’s hand; shooting long strings of white, sticky spunk against the wall of the bathtub and into the remaining water. Fili released Kili’s cock, knowing his younger brother to be sensitive after cumming, but inserted a second finger into the soaking, clenching entrance before pumping them in and out thickly while Kili quaked and panted limply against the elder.

“F-Fee, w-what are you doing?” Kili asked weakly, too overcome with pleasure to really care any longer as Fili fucked him on his thick fingers.

“This hole just, opened up, when I was rubbing against you. Right as you were about to cum, baby. I think it’s like a pussy because it’s all wet and stretched already,” Fili rasped while his dick twitched insistently against the back of Kili’s tail, needing more friction that it was getting sliding over the blue fish scales.

“I have a pussy? It’s in the back of my tail, I have a fucking dick, Fee,” Kili grunted slightly irritably, much to Fili’s amusement.

“I know, you’re all mer…man, Kili,” he chuckled, “Maybe it’s your asshole, I dunno, but it’s squirting cum at me every time I push my fingers in,” he finished huskily, biting at Kili’s shoulder possessively.

Kili wiggled against Fili’s fingers and squeaked, “P-put a third in me, brother,” while his face bloomed red, he didn’t know why he was so embarrassed about his lover fingering his…slit…Fili fingered his tight pucker all the time while he was in human form; but this felt so…different, so good, unlike anything he had felt before, even when Fili pegged his prostrate gland harshly just like Kili liked it.

Kili shivered and moaned in bliss when Fili stretched the brunette’s wet slit open with a third finger, feeling his spent cock already twitching and awakening again, despite the soreness he felt from just having orgasmed.

“Can I…can I fuck you, Kee? In here?” Fili asked, wiggling his fingers inside his little brother for emphasis and drawing more pleasured wails from the noisy merman.

“Y-yes,” Kili panted out, barely aware of his surroundings anymore as Fili took the merman apart on his fingers in ways he had never done before.

Fili withdrew his fingers with a low groan from his little brother and grabbed his thick cock to line the fleshy head up with Kili’s dripping hole. He pushed in slowly, testing, but didn’t need to be so careful; Kili keened and arched his back, pushing himself all the way down onto Fili’s girth in one thrust with an obscenely loud moan. Fili wrapped one arm around the thrashing merman’s chest and grabbed onto Kili’s thin waist with his other hand, before pulling back and snapping his hips forward, whimpering when he slotted himself into his brother again in a delicious push and pull.

Fili pushed home again and again while Kili only begged for more, harder, faster, until the elder had pinned the younger up against the edge of the bathtub and was driving into him forcefully while the merman squealed shamelessly as his own hardness rubbed against the slippery, cool porcelain. Kili’s slit fluttered around Fili’s cock, spasming and tightening, seemingly on the edge of another orgasm and Fili fisted Kili’s sensitive prick once more and rubbed at it fiercely while continuing to fuck into his brother roughly, utterly wrecking the merman on his fat cock.

"O-oh God Fee, oh God,” Kili wailed to the ceiling, before gasping and losing his voice for moment as he came spectacularly against the side of the bathtub, into Fili’s fist.

As the merman came, his entrance tightened and clamped down around Fili’s sex and the blonde pushed himself in one last time before muffling his screams with his teeth against Kili’s shoulder as he poured his release deep into his little brother’s squirting slit.

Kili was shuddering and whimpering in over-sensitivity and Fili pulled out gently before laying back against the chilly bathtub to catch his breath and cradling his equally exhausted baby brother in his arms. Their skin stuck together with sticky sweat and Fili winced as Kili shifted against him and their flesh made odd squelching noises in the near-empty bathtub. The elder chuckled lightly and shook his head, they were ridiculous, before leaning over to turn the faucet on once more while Kili groaned but obligingly pulled the stopper from the drain so they could re-fill the bathtub with clean, warm water again.

“So I guess we don’t have to wait while I’m a merman anymore, huh?” Kili grinned cheekily at the still-panting elder while flicking his blue tail fins ticklishly over Fili’s feet.

“Ugh, stop it, Fishy,” Fili grumped before smiling truly, softly, while his sapphire eyes lit up happily, “Guess not, baby,” he replied warmly.

Kili sighed and rested back against Fili’s chest once more as the tub filled and splashed his fins languidly against the rippling water, “That was amazing, Fee, I’ve never felt anything like that,” he murmured shyly while his cheeks flushed red.

Fili squeezed his arms around Kili in a hug, “It was,” he agreed, “Kee?”

“Yeah?” Kili muttered while twisting to the side to burrow his face into Fili’s arm.

“I love that you’re a squirter,” Fili whispered in the quiet bathroom, needing his lover to know how amazing he truly was, “I love all of you, everything about you is beautiful; but God, baby, now that I’ve known you like this,” he bit his lip and took a deep breath before continuing, “You’re so fucking amazing, Kee,” he finished passionately.

Kili grinned against Fili’s arm and blushed even deeper, if that was possible, before mumbling out, slightly muffled by his elder brother’s flesh, “Thanks Fee, love you too.”

Fili took a deep breath and sighed in content before shutting the faucet off with his toes and sliding deeper into the bathtub, holding Kili to him chest closely, and eventually falling into a light, warm nap with the happy merman humming in his arms.


End file.
